Behavior

amp-iframe has several important differences from vanilla iframes that are designed to make it more secure and avoid AMP files that are dominated by a single iframe:

An amp-iframe may not appear close to the top of the document (except for iframes that use placeholder as described below). The iframe must be either 600 px away from the top or not within the first 75% of the viewport when scrolled to the top, whichever is smaller.

An amp-iframe must only request resources via HTTPS, from a data-URI, or via the srcdoc attribute.

An amp-iframe must not be in the same origin as the container unless they do not allow allow-same-origin in the sandbox attribute. See the "Iframe origin policy" doc for further details on allowed origins for iframes.

Usage of amp-iframe for advertising

amp-iframemust not be used for the primary purpose of displaying advertising. It is OK to use amp-iframe for the purpose of displaying videos, where part of the videos are advertising. This AMP policy may be enforced by not rendering the respective iframes.

amp-iframe enforces sandboxing and the sandbox is also applied to child iframes. This means landing pages may be broken, even if the ad itself appears to work.

amp-iframe does not provide any mechanism to pass configuration to the iframe.

amp-iframe has no fully iframe controlled resize mechanism.

Viewability information may not be available to amp-iframe.

Attributes

src

The src attribute behaves mainly like on a standard iframe with one exception: the #amp=1 fragment is added to the URL to allow
source documents to know that they are embedded in the AMP context. This fragment is only added if the URL specified by src does
not already have a fragment.

sandbox

Iframes created by amp-iframe always have the sandbox attribute defined on them. By default, the value is empty, which means that they are "maximum sandboxed". By setting sandbox values, one can opt the iframe into being less sandboxed. All values supported by browsers are allowed. For example, setting sandbox="allow-scripts" allows the iframe to run JavaScript, or sandbox="allow-scripts allow-same-origin" allows the iframe to run JavaScript, make non-CORS XHRs, and read/write cookies.

If you are iframing a document that was not specifically created with sandboxing in mind, you will most likely need to add allow-scripts allow-same-origin to the sandbox attribute and you might need to allow additional capabilities.

Note also, that the sandbox applies to all windows opened from a sandboxed iframe. This includes new windows created by a link with target=_blank (add allow-popups to allow this to happen). Adding allow-popups-to-escape-sandbox to the sandbox attribute, makes those new windows behave like non-sandboxed new windows. This is likely most of the time what you want and expect. Unfortunately, as of this writing, allow-popups-to-escape-sandbox is only supported by Chrome.

Once this message is received, the AMP runtime tries to accommodate the request as soon as possible, but it takes into account where the reader is currently reading, whether the scrolling is ongoing and any other UX or performance factors. If the runtime cannot satisfy the resize request,
the amp-iframe will show an overflow element. Clicking on the overflow element will immediately resize the amp-iframe since it's triggered by a user action.

Here are some factors that affect how fast the resize will be executed:

Whether the resize is triggered by the user action.

Whether the resize is requested for a currently active iframe.

Whether the resize is requested for an iframe below the viewport or above the viewport.

Iframe with placeholder

It is possible to have an amp-iframe appear at the top of a document when the amp-iframe has a placeholder element as shown in the example below.

The amp-iframe must contain an element with the placeholder attribute, (for instance an amp-img element) which would be rendered as a placeholder until the iframe is ready to be displayed.

Iframe readiness can be known by listening to onload of the iframe or an embed-readypostMessage, which would be sent by the iframe document, whichever comes first.

Iframe viewability

Iframes can send a send-intersections message to their parents to start receiving IntersectionObserver style change records of the iframe's intersection with the parent viewport.

Note: In the following examples, we assume the script is in the created iframe, where window.parent is the top window. If the script lives in a nested iframe, change window.parent to the top AMP window.

The intersection message would be sent by the parent to the iframe when the iframe moves in or out of the viewport (or is partially visible), when the iframe is scrolled or resized.

Tracking/analytics iframes

We strongly recommend using amp-analytics for analytics purposes, because it is significantly more robust, complete and an efficient solution which can be configured for a wide range of analytics vendors.

AMP only allows a single iframe that is used for analytics and tracking purposes, per page. To conserve resources, these iframes will be removed from the DOM 5 seconds after they loaded, which should be sufficient time to complete whatever work is needed to be done.

Iframes are identified as tracking/analytics iframes if they appear to serve no direct user purpose such as being invisible or small.

Guideline: Use existing AMP components over amp-iframe

The amp-iframe component should be considered a fallback if the required user experience is not possible by other means in AMP, that is, there's not already an existing AMP component for the use case. This is because there are many benefits to using an AMP component tailored for a specific use-case such as:

Better resource management and performance

Custom components can provide built-in placeholder images in some cases. This means getting, say, the right video thumbnail before a video loads, and reduces the coding effort to add a placeholder manually.

Built-in resizing. This means that iframe content with unpredictable size can more often appear to the user as if it were native to the page, rather than in a scrollable frame

Other additional features can be built in (for instance, auto-play for video players)